Speed indicator



T. FARMER. Jn. SPEED INDICATOR, APPLlc/Tlorg r|LD;AuG.'z|,"1919.

Patented May 23, 1922.y

0%71/@0 Inventor By t'torney UNITED STATES PATENTl OFFICE.

THOMAS FARMER, JR., OF'NEW YORK, N. Y.

.SPEED INDICATOR.

Application iled August 21, 1919. Serial No. 319,021.

Taj/@ZZ fio/tom 'it may concern .7

Be it `known. thatI, THoaraslTnRMnR, Jr., U ot the United States, residing at lowingbeingW a full, clear, and exact dis-v closure ot the `one 'form oiZ my invention which I at present deem preferable.

For a detailed description ot `the'present 'orin ot my invention, reference may be had to the following specilication and to the aceoingninying drawing forming a part thereof.

My invention relatesto speed indicators designed to sh w theeynchronous speed of two shafts which is desired to connect towether in a certain gear ratio, and it consi 'r ot adjacent speedometers driven respectivelyy by the shafts that are to be connected, the graduation on the speedometer of one shaft being equal to that ot the other shaft .ultiplied by the gearing ratio. Thereby e two slgieedometers will show the same ure at a time when their relative speeds are in the correct ratio. In general one speedometer represents the speed of its driving shaft but the other represents the speed of its drivingshatt multiplied by a 'factor corresponding` to the speed relation of the two shafts. I have illustrated my invention by speed indicators applied respectively to the jack shaft and the propeller shaft ci an automobile.

These two shafts are at certain times to be connected in the intermediate gear ratio. Since the former shaft then 'has the higheil speed., its speedometer is provided with graduations which correspond to those ol" the propeller-.hatt speedometer multiplied by the intermediate gear ratio. Thereby both speedometers will show the same ligure-say tive miles per hour on the propeller speedometer-when their relative speeds are in the gearing ratio. I also show a second set of graduations indicating, on the same principle,y the syncbronism ot the propeller shaft and clutch shatt.

Referring to the accompanying drawing, l) represents the propeller-shaft and E the jack-shaft ot an ordinary transmission gearing ot an automobile. C is the clutch-shaft which is permanently geared to thejackshait in a lixed ratio by the wheels c and c. F is the gear case. The propeller-shaft, by means ot the gears d, g, and 'flexible shaft rh city, borough ot Manhattan, inv

(Jr, drives a speed indicator A and a similar adJacent indicator Bis driven by the jackshaft through gears e, 7L and flexible shaft H. These two speedometers may be of any desired kind, such as are now well known on automobiles provided they are of the vibrating type such as I have indicated in my drawing. In practice I am employing the well-known speedometer of the Waltham lVatch Company, (Tesla Patent No. l ,209,359,) which it is not necessary to illustrate, but which, it may be said, has itsvibrating member operated in one direction by a spring and in the opposite direction by the air-film drag of a continuously rotating member driven usually from the propeller shaft. I is a stationary marker under which move the graduations on the respective speedometers. i y

The graduations on A indicate, as usual, the yvehicle speed-say from zero to 80 lvl. P. H. On B, however, the graduations on the lower edge ot the scale are wider than those on A, in a ratio proportional to the gea1 ratio ot the two shafts when engaged tor intermediate gearing. Hence, if both scales indicatesay live, it means that the propeller-shaft 4has a speed corresponding to a vehicle speedot tive M. P. I-I. but that the jack-shaft has a speed higher than that of the propeller-shaft in the ratio of the calibration widths, which is also the speed ratio of the two shafts when the teethv of the intermediate gears are at synchronous speed. So at that time the `gears may be engaged without clashing. Assume that the car has been started on low gear, the jackshaft indicator then showing a much higher figure than the car. speed, and it is desired to shift to intermediate. `The clutch is opened, the gears disengaged, and the spinning jack-shaft slows down rapidly until its scale shows the same ligure under the marker that the propeller-shaft shows, then it is apparent that, with respect to thatparticular vehicle speed, the jack-shaft speed has a ratio corresponding` to the intermediate gear ratio-e g. lf3-and so the intermediate zgears may be safely put into mesh.

On the upper edge of speedometer B is another set of graduations which are also artificial, not representing the speed of the jack-shaft which drives the speedometer, but the speed of the clutch-shatt (to which the jack-shaft is permanently geared) in terms ot the vehicle speed. That is, of

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course, due to the fact that the-elutch-shaft is to be connected directly to the propellershaft for the high condition. ln this case also the jaclcshaft indicator' does not represent the jack-shaft speed, but represents that speed multiplied by a factor corresponding to the speed ratio of the two shafts, that factor now being the gear ratio between the jack-shaft and the clutch-shaft which is to engage the propeller-shaft and therefore must show the same speed as the propeller'- shaft when it is in condition to engage it. ln this case the computation aforesaid makes the graduations of the same width as those of the indicator A. It is apparent that additional graduations may be added for additional gearing ratios and also that the speedometer B might be operated by the clutch instead of the jaclcshaft with appropriate corrections for the permanent gear relation between them. Moreover while l have shown the indicator' t as driven directly by the propeller shaft, it may be equivalently driven by a wheel or other rotary part that will similarly represent the 'f1/'chicle speed. An important advantage in my present apparat-us is that the saine marker 'which shows lvehicle speed may also be used to show the synchronism of the parts which are to be engaged in shifting the gears. That eliminates the confusion which is liable to occur when a multiplicity of indications are to be read from the same instrument. It moreover greatly simplifies the mechanical construction of the duplex indicator.

"What l claim as new and desire to secure by Letters Patent is:

l. The combination of two shafts arranged to be disengaged and reengaged with respect to each other, and two adjacent vibrating speed indicators driven by the respective shafts, one indicator being graduated to represent the speed of its driving shaft and the other to represent the speed of its driving shaft multiplied by a factor corresponding to the gearing relation between the two shafts.

2. The combination with two rotary shafts of two adjacent indicators driven by theref spective shafts and a stationary marker with respect to which both indicators are graduated.

3. The combination with two rotary shafts arranged to operate at different speeds, two vibrating speedometer-s driven by the respective shafts and a stationary marker with respect to 'which both indicators are graduated7 one of them directly and the other by a multiplying factor correspmiding to the speed ratio of the two shafts 4t. The combination with two rotary shafts arranged to run at different speeds of two speed indicators driven by the shafts respectively and a common marker7 the two indicators having differently spaced graduations corresponding to the speed difference between the two shafts.

Signed at New York, county and State of New York, this 19th day of August, 191).

'FHOM A w li ARMEE, Jn. 

